In a system to save contents to a server and allow the contents to be viewed with a client, there exists a method in which the client uses a cache that temporarily stores the contents as a method of increasing the speed of access to the content and reducing the load of a network. It should be noted that the contents may include a motion image, a still image, a sound (audio), and the like.
Methods for deleting contents in a cache include a method for deleting contents in such an order that older contents are deleted first (Least Recently Used), a method for deleting contents in such an order that newer contents are deleted first (Most Recently Used), and a method for deleting contents in such an order that contents less frequently used are deleted first (Least Frequently Used). There is also a method of preferentially deleting contents which belong to a genre of a low viewing tendency on the basis of a viewing history (for example, see Patent Document 1).
When contents are randomly accessed in the method for deleting contents in such an order that older or newer contents are deleted first, it is highly possible that contents to be accessed are already deleted, and the cache cannot efficiently store contents.
In contrast, in the method of deleting contents in the cache on the basis of the usage frequency and the viewing history, contents which are less likely to be used in the future based on the usage in the past are preferentially deleted, and therefore, the cache can efficiently store the contents.